With increasing frequency, physicians need to gain access to the uterine cavity for such procedures as therapeutic abortion, insertion of intrauterine devices, and evaluation of the endometrium. Entry into the uterine cavity is via the uterine cervix, a fibromuscular organ intercalated between the vaginal vault and the uterus.
In its usual state, the cervical canal has a diameter of approximately 2-4 millimeters (mm.) which is too narrow to allow sufficient access. Traditionally, the cervical canal has been mechanically expanded with a series of sequentially graded metal rods. Although effective, the rods have several drawbacks including:
(1) considerable skill and experience are required for safe use;
(2) overly rapid dilation can lead to significant tissue trauma; and
(3) they are painful, often requiring anesthesia prior to use.
The development of hygroscopic dilators has significantly reduced the need for rapid mechanical dilation of the cervical canal. An early example of a hygroscopic dilator was the Laminaria tent. This device is formed as a dry piece of seaweed root (Laminaria japonica) shaped generally like a large toothpick. When exposed to moisture, it gradually swells to several times its original diameter. This atraumatically and painlessly dilates the cervical canal.
More recently, a variation of such hygroscopic dilators was developed in the form of a dilator formed from a synthetic material such as a hydrogen exhibiting the necessary hygroscopic characteristics and available under the trade name "DILAPAN" from Gynotech, Inc., Lebanon, N.J. See U.S. Pat. No. 4,480,642 issued Nov. 6, 1984. Such synthetic dilators exhibited several advantages over Laminaria tents, including:
(1) the Laminaria tent inherently included small surface crevices rendering them incapable of complete sterilization; by contrast, synthetic dilators are entirely synthetic, allowing them to be completely sterilized;
(2) Laminaria tents inherently have rough surfaces which may cause tissue tearing upon insertion or removal; by contrast, synthetic dilators have smooth surfaces which reduce the risk of tissue tearing;
(3) the supply and price of organic raw materials from which Laminaria tents are produced fluctuate due to environmental factors; by contrast, synthetic dilators are produced by a synthetic process, leading to a stable supply and price;
(4) as Laminaria tents are hand crafted from a natural material, their initial diameter varies; by contrast, synthetic dilators are produced with close tolerances;
(5) Laminaria tents have a less uniform and relatively slower rate of swelling as compared to synthetic dilators.
Use of both types of hygroscopic dilators has become widespread throughout the United States. Because of the earlier availability of the Laminaria tent, it became more widely used. However, synthetic dilators are becoming more competitive with Laminaria tents for comparative reasons set forth above.
Both types of dilators are cylindrical. In contrast, the usual instruments employed in the past for insertion and removal of the dilators, for example, Bozeman uterine packing forceps and ring sponge clamps, have flat grasping surfaces. As a result, these instruments are unable to securely grasp the dilators. The resulting lack of control over the dilators by the manipulating forceps or the like may lead to several adverse consequences, including:
(1) an increased risk of perforation of the cervical or uterine tissue; and
(2) the dilator must be discarded if it is accidentally dropped or contaminated, for example, by touching the vaginal walls, either occurrence tending to increase the expense of the dilators and associated procedures.
With the earlier developed Laminaria tent, forceps were developed for specifically facilitating insertion of the Laminaria tent into the uterine cervix, as set forth in U.S. Pat. No. 4,192,313 issued Mar. 11, 1980 to Ogami. The Ogami forceps were in the form of interconnected members having fore ends of the members including a plurality of elongated grooves forming edges for clamping onto the Laminaria tent to facilitate its insertion into the uterine cervix.
The Ogami forceps were superior to previously employed devices such as the Bozeman uterine packing forceps and ring sponge clamps because the inwardly tapered grooved surfaces of the Ogami forceps permitted improved clamping on the Laminaria tents. However, there was found to remain a need for further improvements in such forceps to further facilitate their use in inserting hygroscopic dilators into the cervical canal and preferably for also retracting the dilators when necessary.